It is, in fact, the oldest one in the world (1762). Having said that, a real indicator is McSorley's. There's a line outside, just to get in, in the mornings. These folks are already smashed and it's not even noon.
Like Halloween, the time of the year is not kind to revelers so oftentimes there's an impatience to get through it but, even then, the scale is pretty impressive.